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When I was a kid I used to watch
a lot of sci-fi movies

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in which there were 
genetically modified beings

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to have superior bodies or intelligences.

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I remember Blade Runner's replicants.

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They really caused an impression on me.

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Today, science is not that far
from that fiction.

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In 2018 in China,

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twins were born whose embryos 
were genetically modified

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with a mutation that would make them

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HIV-resistant,

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the virus that causes AIDS.

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Since the mid-20th century

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we know that the genes of all organisms

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are made up of DNA molecules,

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also known as 
"the molecules of life".

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Genes determine that a plant 
has large or small leaves,

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that an insect has wings or not,

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or that a person has 
brown or grey eyes.

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When the chemical composition
of a gene's DNA changes,

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the characteristics this gene defines
also change.

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For many years, changing the chemical 
composition of DNA in humans

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had been very, very difficult.

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But everything changed recently

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when a revolutionary technique 
called CRISPR was developed.

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The birth of the twins in China

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is the beginning of a new era 
in modern medicine.

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Genetic manipulation of 
human beings is already possible.

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Maybe some of you
already heard of this technique.

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What is CRISPR?

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It is much easier to modify 
embryonic cells with CRISPR

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than to explain the meaning
of the acronym.

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For the curious, CRISPR means

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"clustered regularly interspaced
short palindromic repeats."

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Unfathomable, I know.

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I would simplify it like this:

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if an organism's DNA contains 
all necessary instructions

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to build that organism,

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CRISPR is a text editor that can 
easily change those instructions.

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I was one of the first scientists

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dedicated to CRISPR research.

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My discipline is not genetic engineering 
but microbiology.

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I study how bacteria defend themselves
against their viruses.

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Yes, it's not just human beings
and animals that get infected by viruses.

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Also bacteria.

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CRISPR is the immune system 
these little single-celled guys have

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to defend against viruses.

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In 2008, together with my colleague 
Erik Sontheimer,

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we found out how CRISPR works.

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Bacteria program CRISPR to cut viral DNA,

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in that way destroy the virus 
and cure themselves of the infection.

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In the publication of this work 
we proposed that this mechanism,

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that evolved naturally in bacteria,

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could be transplanted 
to other organisms

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for medical and biotechnological
applications.

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In particular, we thought
it could be used

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for the modification of human genes.

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Why? Because two steps
are required to modify genes.

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First, we have to cut the gene 
we want to modify.

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And second, we have to repair 
or fix that gene

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with a DNA sequence that is the one
we want to introduce,

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which would modify the gene.

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Repairing cut DNA is relatively simple

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because cells can do it themselves.

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Any damage to the DNA 
immediately triggers mechanisms

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that repair it with other DNA 
from a similar sequence.

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This other DNA, similar to the cut DNA, 
is called template DNA.

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And it's very easily introduced 
by a researcher

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after cutting the DNA with CRISPR.

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What was always very difficult to achieve
was to develop a technique

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that would cut specifically 
a gene among all the genes

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that we have in the cells.

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So, along with Feng Zhang, 
an expert in genetic engineering,

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we decided to transport the CRISPR system 
from bacteria to human cells

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to have it do the same 
it does in bacteria:

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cut DNA specifically.

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We program CRISPR to cut 
the human gene EMX1,

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and we repaired it with a template DNA

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introducing three
modifications to the DNA.

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After several tests 
to fine-tune the technique

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we got mutant cells 
which had all the three modifications

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that we designed ourselves.

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We published our work in 2013

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and because of the efficiency 
and the simplicity of the technology,

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it was adopted by research labs

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around the world.

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It was the beginning
of the CRISPR revolution.

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This new technology has 
two fundamental problems.

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One is technical and the other, ethical.

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The first, the technical one, is 
that CRISPR can have "side effects".

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What does that mean?

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That CRISPR can cut not only 
the gene you want to cut,

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but also another gene,
therefore introducing mutations

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you don't want to introduce.

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To reduce this risk 
CRISPR is usually programmed

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in several different ways.

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And only those

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with minimal and acceptable risk
of side effects are adopted.

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Taking these precautions, 
today CRISPR is already being used

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for multiple medical applications.

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Although all of them are still 
in an experimental phase.

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For example, immune system cells
can be modified

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to attack cancer cells 
and therefore attack tumors.

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Certain lymphomas and leukemias
are starting to be treated

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with this technology.

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Research is also after new therapies

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to cure genetic diseases.

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CRISPR is injected to modify
the defective gene

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that causes that disease and correct it,

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and in this way restore 
the functions of the organs

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that are affected by the deficient gene.

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In other fields, it is already beyond 
the experimental stage

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and it's making significant impact.

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In agriculture, for example, 
CRISPR can be used

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to have crops with higher yields,

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resistant to certain 
environmental conditions.

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Livestock can be modified with CRISPR

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to increase meat production

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and be more resilient 
certain diseases.

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No doubt CRISPR 
will be one of the technologies

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that's going to help
feeding the world by 2050,

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with its 10 billion inhabitants.

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The second problem, the ethical one, 
is much more serious.

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Embryonic cell manipulation 
that would result

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in the creation of
genetically modified human beings

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has been disapproved by all 
scientific academies worldwide.

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Because the modification of embryos 
has a lot of troubles.

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One is risk.

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In all medical interventions 
there are risks.

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Another problem is the lack 
of consent.

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The person being born
from embryos modified with CRISPR

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can't decide.

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It is possible to imagine children 
blaming their parents

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for having introduced them traits 
they didn't want to have.

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There's also the problem 
of inequality.

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Not everyone will have the resources 
to access this technology,

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which would widen the gap even more 
between the poor and the rich,

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whether it's people or countries.

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But the most complicated question is:

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in which cases is acceptable 
the "genetic improvement" of humans?

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From a religious point of view 
probably never.

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From a medical point of view 
it would only be accepted

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if it is possible to cure genetic diseases

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that have no other treatment available.

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But what will happen if future parents 
want to give their children advantages

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by changing their genes?

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Currently, doping is not accepted 
in athletes.

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Would we allow competitions with athletes

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that were genetically modified?

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The case of the CRISPR twins 
makes it clear to us

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how complex the problem is.

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The researchers who performed 
the treatment of the embryos

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justified it by labeling it 
as AIDS prevention,

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but the rest of the 
scientific community

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saw it as a clear example 
genetic improvement,

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which was also carried out

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regardless of
the possible side effects,

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and not even calculating
the risks it might have.

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The disapproval didn't just come 
from the scientific world.

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Researchers involved 
were sentenced to three years in prison.

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Today we all agree that 
the experiment carried out in China

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was completely irresponsible 
and premature.

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But it made it clear to us
that genetic modification of humans

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is possible and that it will certainly 
be part of the world to come.

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It was the take-off of a ship to a future,
and there is no turning back.

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While there's still a long way to go 
to know what genes

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we have to change in people

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to create the "replicants" 
of Blade Runner,

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CRISPR gave us the tool to do it

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when we have that knowledge.

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But we can't wait arms crossed.

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Now it's time to start 
discussing and debating

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how we are going to use
this new technology.